Viticultural Performance of Five Merlot Clones in Oakville, Napa Valley

Abstract

Five certified clones of Merlot from Foundation Plant Services (FPS), University of California, Davis, were evaluated for viticultural performance in Oakville, Napa Valley. Vine yield components (cluster number, cluster weight, clusters per shoot, berries per cluster, and berry weight), fruit composition (Brix, pH, titratable acidity), potassium (K) concentration, and vegetative growth parameters (pruning weight and shoot weight) were measured over five growing seasons, 1997 to 2001. Yield, berries per cluster, berry weight, and cluster weight varied significantly among clones, and all yield components varied significantly from season to season. FPS 8 yielded 35% less than clones FPS 1, 3, and 6. FPS 9 showed the most erratic yield pattern over seasons. The number of berries per cluster was primarily responsible for yield differences. Fruit composition parameters pH and K concentration varied significantly among clones, with FPS 8 having both the highest pH and K concentration. Brix concentration at harvest did not significantly differ among clones despite yield differences. Vegetative growth differed significantly among clone, with FPS 8 having the greatest pruning weight and FPS 1 the least. Yield to pruning weight ratios were lowest for FPS 8 and highest for FPS 1.